Boiler feedwater system



Jan. 1, 1952 R. F. SCHAUB BOILERFEEDWATER SYSTEM Filed Sept. 9, 1948 Patented Jan. 1, 1952 2,581,146 BOILER FEEDWATER SYSTEM Robert F. Schaub, Chicago, Ill., assignor to Fred H. Schaub Engineering 00., Inc., Chicago, Ill., a corporation of Illinois Application September 9, 1948, Serial No. 48,453

6 Claims. (Cl. 237-9) My invention relates to an improved boiler feedwater system in which boiler feedwater is heated by the returning condensate before be ing pumped into the boiler.

.. In my Patent 2,420,624, issued May 13, 1947- and entitled, "Boiler Feed-Water System, I have described and claimed a boiler feed-water system having a heat exchanger through which condensate travels and elements to control condensate fiow for most effective operation.

In accordance with the present invention this control is achieved in an improved manner capable of operating effectively when the system is started from the shut-down condition It is accordingly the general object of the present invention to provide an improved boiler feedwater system wherein condensate is used to preheat the feedwater in an efiective manner andwhich is capable of operating effectively from the shut-down condition.

A further object of the present invention is to provide an. improved boiler feedwater system in which the back pressure in the heat exchanger for heating the boiler feedwaterirom returning condensate is maintained at the optimum value under all conditions, including starting from the shut-down condition. Yet another object is to provide a completely automatic boiler feedwater system wherein back pressure in the heat exchanger is controlled at the value permitting most effective operation and in which a quick air purge and rapid condensate removal is automatically achieved when starting from the shut-down condition.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation may best be understood by reference to the following description taken in connection with the accompanying drawing, in which: 7

Figure l is a diagrammatic view of a system embodying the present invention;

Figure 2 is an enlarged fragmentary sectional view of the pressure regulating mechanism of Figure 1; and,

Figure 3 is an enlarged fragmentary sectional view of an alternative embodiment of the pressure regulating mechanism.

In the system of Figure 1, a steam boiler I 6 which may be of conventional construction supplies steam to a main II, which may be con nected to one or more steam consuming loads indicated at I2. ,The loads I2 may be any desired type of apparatus which consumes steam the like.

during operation such, for example, as steam heated molds or presses for rubber or plastic, laundry processes, jacketed kettles, driers, or Condensate from the load is returned to the return line I3 through a trap device indicated at Id. The trap device may be a conventional steam trap or any other desired type of apparatus which will function tosubstantially prevent live steam from flowing from the load through the return conduit I3. Such trap devices will prevent the passage of any substantial quantity of live steam but even when. in good working order will pass some live steam along with the condensate.

Feedwater is supplied to the boiler I0 through a conduit I5 into which it is pumped by a pump or the like indicated at I6 and driven by a motor II. It will be understood that operation of the feedwater pump is controlled in a conventional manner by devices not shown to maintain the water in the boiler at a substantially constant level.

The feedwater is heated by the returning. condensate and such live steam as may pass through trap device I4, before being pumped into the boiler and for this purpose a heat exchanger is connected between the pump and the boiler. As shown, the heat exchanger comprises a shell I8 connected througha pipe 20 to the pump outlet to receive water from the pump. The feedwater pipe I 5 is connected to the shell to receive feedwater therefrom and conduct it to the boiler.

Within the shell there is arranged a bundle of tubing I9 connected at one end to the pipe I3 to receive condensate therefrom and at its op-' posite end to an' outlet connection 2|. In operation condensate and steam flowing through the tube bundle I9 supplies heat to the feedwater flowing around the bundle through the shell I8 to bring the feedwater to elevated temperature. approximating that of the condensate return.

Condensate flowing out of the tube bundle is vented to atmosphere through a vent pipe 26 and excess water may be discharged therefrom through an overflow pipe 21. A conduit 3! connects the lower part of the tank to the feedwater pump 16.

With a system as so far described, the pressure on the condensate will. be substantially reduced when it passes the trap so that a substantial amount of condensate will flash into steam. This steam, together with the live steam passing the trap, causes the mixture to flow rapidly through the tubing l9 so that a relatively low heat recovery is obtained in the heat exchangers. Furthermore, fluctuations inflow in response to variations in load demand cause the discharge characteristics of the traps to vary so that under some conditions they may pass excessive quantities of live steam.

According to the present invention, the fore- 7 going difiiculties are overcome by maintaining substantially constant trap characteristics to minimize flashing and to increase retention time in the heat exchanger by maintaining a constant back pressure on the discharge from the tubingbundle 19. As seen best in Figure 2, this is accomplished by means of the'regul'ator shown generally at 28 which is interposed between the heat exchanger 18 and the feedwater supply tank 23. Asshown, this regulator includes an enlarged portion 2m in pipe 2l' which has a diaphragm dividing it into a lower chamber 2lc and an upper chamber 2 Id. A poppet type valve plunger 29 seats on the'diaphragm to control the passage of fluid from lower chamber 21:: to upper chamber 2|d. The position of valve 28 is controlled by the bellows 3fl"which are suitably anchored at one end by 'meansnot shown,to cause shifting movements of the valve 29 in accord with the volume of the fluid entrained in the bellows. The be1lo'ws33 is in fluid communication with the pipe 3| which leads to thethermostat bulb 32 located in thepipe 2|.

The valve plunger 29 acts to interpose" increased resistance to fluid flow through pipe '2! as the temperature of bulb 32 rises. Thisis accomplished by reason of the fluid contained within the chamber'defined by bulb 32, pipe 3|, and bellows 3i! which expands as the temperature is increased. 'Since the bulb 32 is located in the pipe 2 I, this bulb partakes of the temperature of the condensate as it leaves the heat exchanger 18. Consequently, as the condensate temperature rises the fluid flow from the heat exchanger is decreased and as this temperature falls-the fluid flow is increased. the condensate flowing through pipe 2] is a measure or. the. pressure within the heat exchanger it, this action acts to tend to maintain constant pressure in the heat exchanger and thereby avoids the undesirable effects described above.

Moreover, when the plant is started from the shut-down condition, the valve plunger 29 assumes the open position associated with the low temperature condition of bulb 32. This allows free flow of air and condensate through the pipe 2! and thereby achieves an initial blowing action providing a quick air purge and rapid condensate removal. The thermostat bulb 32 holds the valve plunger 29 inthe wide open position until condensate return begins to come back hot, at which time the regulator: closes down and maintains the desired constant pressure condition within heat'exchanger [8.

Figure 3 shows an alternative embodiment of Since the temperature of 4 the regulator 28 which is operated by electrical action. In this structure the valve plunger 29 is attached to the magnetic plunger 33 which is in turn supported in part by the sprin 33a. Solenoid 36 encircles plunger 33 and is connected in electrical circuit relationship with the battery 34, thereby causing current flow through solenoid 36 to aid action of spring 33a and regulate the position'of valve plunger 29. The enlarged section 2 lb of pipe 2| defines a cup which receives a temperature sensitive resistance element '35 interposed in the electrical circuit of battery 34 and solenoid 36. This element is made of amaterial having a relatively great increase in-resistance as temperature rises so that the current flow through solenoid 36 increases with decreasedxtemperature. Since the resistance partakes of the temperature of the condensate flow'through portion Zlb of pipe 2|, the mechanism of Figure 3 acts' like the mechanism of Figure 1 and opens the valve plunger 29 'as the temperature decreases. 7

The boiler feedwater system of the present "in:- vention not only operates toregulate the heat exchanger pressure as necessary for most efiective operation, but it also automaticallyprovides a cleansing action when the system is started up. This avoids the need for by-pass connections about the regulator 28- as well as the needfor any manual control when the system is placed inoperation.

While I have shown bulb 32 in a portion of the pipe 2! having no special enlargement and'the resistance 35in an enlarged portion Zlbof pipe 2|. it will of course be understood that the'pipe may be enlarged or not depending on the size of the bulb or resistance mounted ther'ein.

It will of course be understoodthatwhile'l have shown specific temperature'responsiveflow controlling devices, other units for this purpose may be employed if desired.

While I have shown and describedspecific' embodiments of the present invention it' will, of course, be understood that many modifications and alternative constructions may be used without departing from the spirit and scope thereof. I therefore intend by the appended claims to cover all such modifications and alternative constructions as fall within the true spirit and scope of my invention.

What I claim asnew and desire to secure by Letters Patent of the Un itedStates is:

1. In a boiler feedwater system for use with a boiler, a steam consuming load connected to the boiler, and a feedwater pump having an-inlet connected to pump water into the boiler from the inlet, the combination which comprisesawater storage tank'connected to the inlet, a heat exchanger connected between the pump and the boiler to impart heat to the feedwater, a condensate return connection from the load through the heat exchanger to the storage tank to supply heat to the heat exchanger from the condensate, and a flow controlling device interposed be tween the heat exchanger and storage tank responsive to the temperature of the condensate in the heat exchanger to decrease the flowfrom said heat exchanger as said temperature rises.

2. In a boiler feedwater system for use witha boiler, a steam consuming loadconnected to the boiler, and a feedwater pump having an inlet connected to pump water into the boiler from the inlet, the combination which comprises a water storage tank connected to the inlet; a heat exchanger connected between the pump and. the

boiler to impart heat to the feedwater, a condensate return connection from the load through the heat exchanger to the storage tank to supply heat to the heat exchanger from the condensate, and a flow controlling device interposed between the heat exchanger and storage tank responsive to the temperature of the fluid as it escapes from said heat exchanger to decrease the flow from said heat exchanger as said temperature rises.

3. In a boiler feedwater system for use with a boiler, a steam consuming load connected to the boiler, and a feedwater pump having an inlet connected to pump water into the boiler from the inlet, the combination which comprises a water storage tank connected to the inlet, a heat exchanger connected between the pump and the boiler to impart heat to the feedwater, a condensate return connection from the load through the heat exchanger to the storage tank to supply heat to the heat exchanger from the condensate, trap means between the load and the heat exchanger to prevent the flow of live steam from the load to the heat exchanger, and a flow controlling device between the heat exchanger and storage tank responsive to the temperature of the fluid as it escapes from said heat exchanger to decrease the flow from said heat exchanger as said temperature rises.

4. In a boiler feedwater system for use with a boiler, a steam consuming load connected to the boiler, and a feedwater pump having an inlet connected to pump water into the boiler from the inlet, the combination which comprises a water storage tank connected to the inlet, a heat exchanger connected between the pump and the boiler to impart heat to the feedwater, a condensate return connection from the load through the heat exchanger to the storage tank to supply heat to the heat exchanger from the condensate, a flow controlling device interposed between said storage tank and heat exchanger and having movable elements operative when moved to control the resistance to fluid flow therebetween, means defining an enclosed space of variable size and operative to move said elements as said size varies, said last means including a portion positioned to partake of the temperature of the fluid escaping from said exchanger, and a material in said space having volume varying with temperature to increase said resistance to fluid flow as said temperature rises.

5. In a boiler feedwater system for use with a boiler, a steam consuming load connected to the boiler, and a feedwater pump having an inlet connected to pump Water into the boiler from the inlet, the combination which comprises a water storage tank connected to the inlet, a heat exchanger connected between the pump and the boiler to impart heat to the feedwater, a condensate return connection from the load through the heat exchanger to the storage tank to supply heat to the heat exchanger from the condensate, a flow controlling device interposed between said storage tank and heat exchanger and having movable elements operative when moved to control the resistance to fluid flow therebetween, means operative in response to predetermined electric current flow to move said elements, a source of electric current connected to said means, and a temperature sensitive resistance element positioned to partake of the temperature of the fluid escaping from said exchanger and interposed in the electric circuit of said source and said means to increase said resistance to fluid flow as said temperature rises.

6. In a boiler feedwater system for use with a boiler, a steam consuming load connected to the boiler, and a feedwater pump having an inlet connected to pump water into the boiler from the inlet, the combination which comprises a heat exchanger connected between the pump and the boiler to impart heat to the feedwater, a condensate return connection from the load through said heat exchanger to supply heat to the heat exchanger from the condensate, and a flow controlling device positioned to control fluid flow from said heat exchanger and responsive to the temperature of the fluid from said heat exchanger as said temperature rises.

ROBERT F. SCHAUB.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,3Q9,052 Ellis Dec. 6, 1921 2,126,732 Carries Aug. 16, 1938 2,266,947 Arndt Dec. 23, 1941 2,420,624 Schaub May 13, 1947 

